Processor-based systems require a time base in order to operate. This time base can either be an external time base or an internal time base. The time base provides a clock signal that is utilized by the processor-based system to execute various instructions, run internal timers and provide sample clocks to data conversion systems such as analog-to-digital converters and digital-to-analog converters. In some applications, the processor is able to operate at two clock frequencies, a high clock frequency and a low clock frequency. The reason for operating at the low clock frequency is to conserve power when placed in a low power mode or “sleep mode.” However, if the high frequency clock, which is typically a crystal controlled clock, is operated in the low power mode by utilizing a divider, the power consumed by the high frequency oscillator may still be a factor in overall power consumption. To address this problem, some systems provide for a high frequency oscillator for operating in the high frequency mode and a separate low frequency oscillator for operating in the low frequency mode. With the low frequency oscillator, this is typically fabricated with an RC oscillator with no crystal, which both conserves power and eliminates the need for an expensive external component such as the crystal. However, this type of oscillator drifts with respect to temperature and must be re-calibrated at start-up due to the fact that the frequency thereof varies as a function of manufacturing tolerances due to fabrication process variations. As such, some type of calibration procedure must be performed if it is desired to have a known frequency of operation during low power operation. This is required when a part, when operating in the sleep mode, requires certain known timed events to occur, such as “waking up” after a predetermined amount of time has elapsed.